/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.primitives.Primitives;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import javax.annotation.CheckForNull;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A mutable class-to-instance map backed by an arbitrary user-provided map. See also {@link
 * ImmutableClassToInstanceMap}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#classtoinstancemap">{@code
 * ClassToInstanceMap}</a>.
 *
 * <p>This implementation <i>does</i> support null values, despite how it is annotated; see
 * discussion at {@link ClassToInstanceMap}.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtIncompatible
@SuppressWarnings("serial") // using writeReplace instead of standard serialization
@ElementTypesAreNonnullByDefault
public final class MutableClassToInstanceMap<B> extends ForwardingMap<Class<? extends B>, B>
        implements ClassToInstanceMap<B>, Serializable
{

    /**
     * Returns a new {@code MutableClassToInstanceMap} instance backed by a {@link HashMap} using the
     * default initial capacity and load factor.
     */
    public static <B> MutableClassToInstanceMap<B> create()
    {
        return new MutableClassToInstanceMap<B>(new HashMap<Class<? extends B>, B>());
    }

    /**
     * Returns a new {@code MutableClassToInstanceMap} instance backed by a given empty {@code
     * backingMap}. The caller surrenders control of the backing map, and thus should not allow any
     * direct references to it to remain accessible.
     */
    public static <B> MutableClassToInstanceMap<B> create(Map<Class<? extends B>, B> backingMap)
    {
        return new MutableClassToInstanceMap<B>(backingMap);
    }

    private final Map<Class<? extends B>, B> delegate;

    private MutableClassToInstanceMap(Map<Class<? extends B>, B> delegate)
    {
        this.delegate = checkNotNull(delegate);
    }

    @Override
    protected Map<Class<? extends B>, B> delegate()
    {
        return delegate;
    }

    static <B> Entry<Class<? extends B>, B> checkedEntry(final Entry<Class<? extends B>, B> entry)
    {
        return new ForwardingMapEntry<Class<? extends B>, B>()
        {
            @Override
            protected Entry<Class<? extends B>, B> delegate()
            {
                return entry;
            }

            @Override
            public B setValue(B value)
            {
                return super.setValue(cast(getKey(), value));
            }
        };
    }

    @Override
    public Set<Entry<Class<? extends B>, B>> entrySet()
    {
        return new ForwardingSet<Entry<Class<? extends B>, B>>()
        {

            @Override
            protected Set<Entry<Class<? extends B>, B>> delegate()
            {
                return MutableClassToInstanceMap.this.delegate().entrySet();
            }

            @Override
            public Iterator<Entry<Class<? extends B>, B>> iterator()
            {
                return new TransformedIterator<Entry<Class<? extends B>, B>, Entry<Class<? extends B>, B>>(
                        delegate().iterator())
                {
                    @Override
                    Entry<Class<? extends B>, B> transform(Entry<Class<? extends B>, B> from)
                    {
                        return checkedEntry(from);
                    }
                };
            }

            @Override
            public Object[] toArray()
            {
                /*
                 * standardToArray returns `@Nullable Object[]` rather than `Object[]` but only because it
                 * can be used with collections that may contain null. This collection is a collection of
                 * non-null Entry objects (Entry objects that might contain null values but are not
                 * themselves null), so we can treat it as a plain `Object[]`.
                 */
                @SuppressWarnings("nullness")
                Object[] result = standardToArray();
                return result;
            }

            @Override
            @SuppressWarnings("nullness") // b/192354773 in our checker affects toArray declarations
            public <T extends @Nullable Object> T[] toArray(T[] array)
            {
                return standardToArray(array);
            }
        };
    }

    @Override
    @CanIgnoreReturnValue
    @CheckForNull
    public B put(Class<? extends B> key, B value)
    {
        return super.put(key, cast(key, value));
    }

    @Override
    public void putAll(Map<? extends Class<? extends B>, ? extends B> map)
    {
        Map<Class<? extends B>, B> copy = new LinkedHashMap<>(map);
        for (Entry<? extends Class<? extends B>, B> entry : copy.entrySet())
        {
            cast(entry.getKey(), entry.getValue());
        }
        super.putAll(copy);
    }

    @CanIgnoreReturnValue
    @Override
    @CheckForNull
    public <T extends B> T putInstance(Class<T> type, T value)
    {
        return cast(type, put(type, value));
    }

    @Override
    @CheckForNull
    public <T extends B> T getInstance(Class<T> type)
    {
        return cast(type, get(type));
    }

    @CanIgnoreReturnValue
    @CheckForNull
    private static <B, T extends B> T cast(Class<T> type, @CheckForNull B value)
    {
        return Primitives.wrap(type).cast(value);
    }

    private Object writeReplace()
    {
        return new SerializedForm(delegate());
    }

    /**
     * Serialized form of the map, to avoid serializing the constraint.
     */
    private static final class SerializedForm<B> implements Serializable
    {
        private final Map<Class<? extends B>, B> backingMap;

        SerializedForm(Map<Class<? extends B>, B> backingMap)
        {
            this.backingMap = backingMap;
        }

        Object readResolve()
        {
            return create(backingMap);
        }

        private static final long serialVersionUID = 0;
    }
}
